1. Field of the Invention
The invention is related generally to oil field exploration and in particular to use of at least one of multi-component induction measurements and propagation measurements for geosteering and formation evaluation.
2. Description of the Related Art
Electromagnetic induction and wave propagation logging tools are commonly used for determination of electrical properties of formations surrounding a borehole. These logging tools give measurements of apparent resistivity (or conductivity) of the formation that, when properly interpreted, are diagnostic of the petrophysical and other properties of the formation and the fluids therein.
In various environments, such as those having thinly laminated sand-shale sequences or shaly-sand formations, the formation electrical anisotropy becomes important in determining the hydrocarbon saturation from the resistivity measurements. Due to physical complexities of the formation, determining the electrical anisotropy can be complicated.
For example, intrinsic and macroscopic properties may give rise to anisotropy (i.e., directional dependence). Unfortunately, techniques presently available do not adequately provide for characterization of anisotropy while drilling. However, should adequate characterization of anisotropy be available, one should be able to use the characterization information for geosteering (i.e., steering a drill during a drilling process).
There is a need for advanced methods for providing determinations of formation anisotropy. Preferably, the methods should consistently provide accurate and reliable data, be computationally efficient and useful for implementation while drilling a wellbore, thus providing input to geosteering processes.